The amended lawsuit, filed by the late 22-year-old's conservator Bedelia Hargrove, alleges Gordon, 25, of "being out all night on a cocaine and drinking binge" and giving Kristina a "toxic cocktail," reported Us magazine.

"I am deeply saddened by the recent death of Bobbi Kristina Brown. I have filed today an amended complaint against Nicholas Gordon adding a count of wrongful death and for pain and suffering.

"We will leave no stone unturned in seeking justice for Bobbi Kristina Brown," Hargrove said in a statement.

According to the lawsuit, the concoction left her "unconscious" and he "then put her face down in a tub of cold water, causing her to suffer brain damage."

The only daughter of the late Whitney Houston and Bobby Brown, Bobbi Kristina died on July 26, nearly six months after she was found unresponsive in a bathtub of her home. She was buried next to her mother in New Jersey.